Centrifugal process



Nov. 29, 1938. A. u. AYRES ET AL CENTRIFUGAL PROCESS Filed July 22, 1955 FIG. 2

\AAWM /W Patented Nov. 29, 1938 UNITED STATES PATET OFFICE CENTRIFUGAL PROCESS Application July 22,

Claims.

This invention relates to a method and apparatus for effecting centrifugal separation and concentration. More particularly the invention relates to the separation and concentration of substances which have a tendency to be concentrated to a degree at which they effect partial cloggage of the separating appartus, and in this regard the invention contemplates the concentration of such materials as rubber latex, cream or other liquids of similar character.

It is Well known that the most eflicient concentration of emulsions by centrifugal force can be accomplished in a centrifugal separator in which the turbulence of the material being centrifuged is maintained at a minimum. In the attainment of this end, it is frequently desirable to subject the material under treatment to centrifugal force in the form of thin layers.

When an attempt is made to concentrate latex, for example, in a centrifugal separator constructed to attain this principle of operation, difficulty is encountered because of the concentration of a portion of the material to an undesirably high degree with consequent partial cloggage of the spaces between the 'thin layers and resultant coagulation. This effect is most pronounced when the material within the bowl is subjected to a longer period of concentration than in the normal operation. This invariably occurs when the feed is interrupted and the bowl brought to a stop for cleaning.

The invention will be best understood by a reading of the following detailed description with reference to the accompanying drawing in which 35 like reference numerals indicate like parts and in which:

Fig. 1 is a central vertical sectional view through the rotor of a centrifugal machine, certain parts being shown in elevation;

40 Fig. 2 is a horizontal sectional view of the rotor on line 2-2 of Fig. 1, and

Fig. 3 is a horizontal sectional view on line 3-3 of Fig. 1.

The method of operation comprises the steps of treating a substance by passing the same through a centrifugal machine at relatively low capacity and displacing the residue at the end of the centrifugal operation by means of an auxiliary liquid which is admitted to the machine 50 at relatively high capacity, and in order to render the method intelligible .a description of the machine adapted to its practice will follow.

In the several figures, a centrifugal rotor is indicated at Ill. The rotor is of the cylindrical ;5 type and is provided with a base I2 which con- 1935, Serial No. 32,486

veniently may be screw threaded to one end of the rotor. The other end of the rotor i0 is provided with an integral neck M in which are provided the usual discharge passages for constituents of different specific gravities.

The internal body of the neck i4 is recessed to accommodate a dividing wall. It of which the inner edge I8 constitutes a weir over which the light constituent of the separated substances discharges. The outer edge 20 of the horizontal section of the dividing wall It terminates short of the rotor wall to provide a discharge space for the heavier constituent. .A resilient packing member 22 is provided to maintain a seal between the dividing wall 16 and the internally recessed 15 portion of the neck It. This packing member is preferably in the form of a ring which is resiliently held about the upper portion of the dividing wall. A shallow groove may be provided in the dividing wall for positively holding 20 the packing in position. The dividing wall I6 is provided with a plurality of interrupted thread segments 24 fora purpose which will hereinafter become. evident.

Wings 26, of which only-one is shown, cause liquid that fiows through the rotor to slow down to the circumferential speed of the radially inward parts of the rotor to which it. flows.

Discharge passages 28 and 30 are provided in the neck M for the purpose of permitting egress 30 of light and heavy products of separation. The discharge passage 30, of which there may be several, leads to anannular passage formed in the neck M at its outer extremity. A weir or ring dam 32 controls the discharge from the annular passage which it partially defines. Inasmuch as the character of the discharge is controlled by the radial extent of the ring 32 the, same is made readily replaceable. In order to change rings it is only necessary to remove the nut 34 which is threaded to the neck, substitute the ring, and replace the nut 34 with sufiicient force to seal the ring against a packing member 36 which lies against the outer peripheral edge of the neck it.

The interior of the base I2 is substantially in the form of an inverted cone of which a vertical extension is defined by a wall 38 which is inwardly removed from the rotor wall to provide an annular space therebetween. Within the base is a deflecting plug 40 which has a horizontal portion 42 in the form of a disc which is of such diameter as to leave a passage 48 .between its edge and the wall 38. Distributing vanes 44 are attached to the plug 40 at their points of contact therebetween, and a ring 46 may be fixed to the lower edge of the vanes to make the structure more rigid. It will be noted that there are a plurality of these varies and that they extend radially from the plug 40 into contact with the internal surface of the base l2 to define a plurality of distributing passages.

Within the rotor casing ID are a great number of separating wings 50 which are loosely bound together by meansof split rings 50' which pass through apertures in the wings at a. number of spaced points along their length. Each wing is curved as shown in Fig. 2 and extends into contact with the rotor casing in at its outer edge. The inner edges of the wings extend beyond the ring 50' and terminate substantially at the inner edge l8 of the dividing wall it.

Two feed nozzles 52 and 54 project into the base or feed boss [2. The feed nozzle 52 which is concentrically located within the nozzle 54 is of relatively small capacity and is connected with a source, (not shown), of liquid to be centrifugally treated. The nozzle 54, which is threaded to the housing 55 which surrounds the nozzle 52, is of relatively large capacity and is connected with a water main or source of other auxiliary liquid. Any suitable driving means may be connected with the rotor extension 55 for driving the rotor.

In the use of the above-described machine in the practice of the process of the invention a fiuid, latex for example, is fed at normal capacity through the nozzle 52. The inflowing emulsion strikes the distributing hub 40 which deflects the stream of liquid and directs it into the channels formed between the vanes 44. The vanes 44 bring the liquid up to the rotational speed of the rotor before it is discharged through the annular passage 48 formed between the edge of the disc 42 and the side wall 38. The passage 48 is so located that the liquid is fed into the rotor it at a zone well removed outwardly from its axis. The liquid is divided into a plurality of layers by virtue of the wings 55 within the rotor '10.

As the liquid being treated proceeds through the rotor, the lighter constituent fiows inwardly, while the heavier constituent seeks its position adjacent the wall of the rotor. The light constituent is discharged over the inner edge it of the dividing wall l6 and from there it flows through the discharge passage 28 to the exterior of the rotor where it may be collected in any suitable manner. The heavier constituent flows around the outer edge 20 of the dividing wall it, through the discharge passage 30 and over the ring dam 32 to the exterior of the rotor where it may be likewise collected.

After a given amount of liquid has been centrifugally treated to effect concentration, the supply through nozzle 52. is discontinued and before the rotation of the rotor I0 is discontinued,

water or other suitable flushing liquid is fed at a relatively high capacity through the nozzle 54. In this connection it will be noted that the rate of feed of flushing liquid through the nozzle 54 should be in excess of the capacity of the rotor to dischargesaid liquid through the heavy efiiuent discharge outlet 30. If the rate of feed of flushing liquid were sufficiently small to enable all of that liquid to.be'discharged through the outlets 30, flushing liquid would flow directly through the annular passage 48 into the main body of the rotor and directly radially outwardly between the separating wings 50, thus affording it is desired to flush from the rotor in the case of the concentration of latex lies for the most part radially inwardly of the zone of feed 48 of the flushing liquid, the principle of operation embodied in the feed of the flushing liquid at a I rate substantially in excess of the rate at which the latex to be concentrated has been fed and at a rate in excess of the discharge capacity of the rotor through the outlets 30, becomes an especially important feature in connection with such an operation.

An important feature of the invention consists in the provision of a rotor design affording the possibility of prompt flushing after the completion of a given separating or concentrating cycle and the preferred practice of our invention involves the admission of flushing liquid through the nozzle 54 concurrently with or even prior to the discontinuance of feed of the latex or other material to be concentrated through the nozzle 52. This feature of operation is of great importance, for continued rotation of the bowl after the discontinuance of the feed of emulsion through the nozzle 52 tends to effect coagulation of material within the rotor unless this material I the wings 50 radially inwardly incident to the flushing operation. The major portion of the material which requires flushing after a given cycle of operations lies toward the center of the rotor between the wings 50. It is naturally desirable to avoid waste of this material incident to the flushing operation. If flushing liquid were fed into contact with this material from the center of the rotor the material would be diluted with the flushing liquid and a very substantial proportion of it would flow radially outwardly and be discharged through the discharge outlets 35 from which the latex serum is discharged during the normal operation of the machine. Since the material flushed from the bowl is ordinarily fairly concentrated, it is desirable that it be flushed through the lighter effluent discharge outlets 28 rather than through the heavier efiuent discharge outlets 30 in order that it may be collected with the concentrated latex and not with the serum. The operation of flowing the concentrated material between the wings 5i radially inwardly on an underlying layer of flushing liquid has also been found to afiord a much more satisfactory flushing operation than can be attained by feeding the flushing liquid outwardly against this material and thus diluting the entire contents of the rotor. In the use of the bowl in the practice of the invention,

this concentrated material is flowed radially inwardly and discharged from the rotor without being substantially diluted by the underlying of the base portion. The wings 50 and the dividing wall it can be removed conveniently by passing a screw threaded rod through the center of the wing structure to engage the screw segments 24. After contact has been made by such rod and the segments 24, ample leverage is provided for withdrawing the dividing wall I6 and the wings 50. This arrangement provides an assembly which is simple in construction, of few parts, and one which can be torn down readily for the purpose of cleaning.

While the apparatus herein described may find efficient use in the separation or concentration of any liquid comprising'constltuents of different specific gravities, it has nevertheless been described as most particularly adapted for use in separating or concentrating methods pertaining to such substances as latex, which present the peculiar problem of cloggage of the rotor and coagulation of residue therein upon cessation of the centrifugal operation.

This invention is capable of various changes and modifications, and its application is by no means limited to those herein suggested, but further changes and further applications will become apparent to those skilled in the art and it is therefore not intended that the practice of the invention shall be limited in any wise except by the limitations which may be imposed thereon in the subjoined claims.

It will be appreciated from the above discussion that the practice of the invention results in the recovery of latex flushed from the bowl, and which would otherwise be degraded to a less valuable form, together with latex obtained as concentrate in normal operation. It will also be appreciated that the avoidance of cloggage and coagulation greatly simplifies the cleaning of the bowl.

We claim: 1

1. The method of effecting a centrifugal separating operation on materials having constituentstending to coagulate upon quiesence comprising effecting feed of material to be subjected to the separating operation to a rotating centrifugal rotor, subjecting the material within the rotor to centrifugal force and continuously discharging lighter and heavier eflluents subsided from .the rotor through separate discharge outlets, periodically discontinuing the feed of said material to the rotor and substantially concurrently with the discontinuance of the feed of said material and without substantial deceleration of the rotor feeding a flushing liquid through the rotor during such discontinuance of feed of material under treatment, said feed of flushing liquid being at a rate in excess of the discharge capacity of the rotor through its heavier efiiuent discharge outlet and substantially in excess of the rate of feed to the rotor of material to be separated and hence serving to flush ,subsided lighter material inwardly and effect discharge of said lighter material through the lighter efiiuent discharge outlet of the centrifugal rotor.

2. The method of concentrating an emulsion having constituents tending to coagulate upon quiescence comprising effecting feed of emulsion to a rotating centrifugal rotor, subjecting the emulsion to centrifugal force to effect concen tration within the rotor andcontinuously discharging through separate discharge outlets the lighter emulsion phase and a heavier eilluent subsided from the emulsion phase in the rotor, periodically discontinuing the feed of said material to the rotor and substantially concurrently with the discontinuance of the feed of said emulsion and without substantial deceleration ofthe rotor feeding a flushing liquid through the rotor during such discontinuance of feed of material under treatment, said feed of flushing liquid being at a rate in excess of the discharge capacity of the rotor through its heavier efliuent discharge outlet and substantially in excess of the rate of feed to the rotor of material to be separated and hence serving to flush subsided lighter material inwardly and effect discharge of said lighter material through the lighter efiluent discharge outlet of the centrifugal rotor.

3. The method of effecting a centrifugal concentrating operation with respect to rubber latex comprising effecting feed of latex to be subjected to the concentrating operation to a rotating centrifugal rotor, subjecting the latex within the rotor to centrifugal force and continuously discharging through separate discharge outlets a lighter efiiuent consisting of concentrated latex and a heavier efiluent consisting of aqueous phase separated from said concentrate, periodically discontinuing the feed of latex to the rotor and substantially concurrently with the discontinuance of the feed of said latex and without substantial deceleration of the rotor feeding a flushing liquid through the rotor during such discontinuance of latex feed, said feed of flushing liquid being at a rate in excess of the discharge capacity of the rotor through its heavier eflluent discharge outlet and substantially in excess of the rate of feed of latex to the rotor and hence serving to flush concentrated latex inwardly and effect discharge of said latex through the lighter eflluent discharge outlet of the centrifugal rotor.

4. The method of effecting a centrifugal separating operation on materials having constituents tending to coagulate upon quiescence comprising effecting feed of material to be subjected to the separating operation to a rotating centrifugal rotor, subjecting the material within the rotor to centrifugal force and continuously discharging lighter and heavier effluents subsided from the rotor through separate discharge outlets, periodically discontinuing the feed of said material to the rotor and substantially concurrently with the discontinuance of the feed of said material and without substantial deceleration of the rotor feeding a flushing liquid through the rotor from a zone thereof lying radially outwardly of the zone of subsided lighter material within the rotor during such discontinuance of feed of material under treatment, said feed of flushing liquid being at a rate in excess of the discharge capacity of the rotor through its heavier efiluent discharge outlet and substantially in excess of the rate of feed to the rotor of material to be separated and hence serving to flush subsided lighter material inwardly and effect discharge of said lighter material through the lighter eflluent discharge outlet of the centrifugal rotor.

5. The method of effecting a centrifugal separating operation on materials having constituents tending to coagulate upon quiescence comprising effecting feed ofmaterial to be subjected to the terial and without substantial deceleration of the rotor feeding a flushing liquid through the rotor 4 during such discontinuance of feed of material under treatment, said feed of flushing liquid being at a rate in excess of the discharge capacity of the rotor through its heavier eifiuent discharge outlet and substantially in excess of the rate of feedto the rotor of material to be separated and hence serving to flush subsided lighter material inwardly and efiect discharge of said lighter material through the lighter eflluent discharge outlet of the centrifugal rotor.

ARTHUR U. AYRES. ASHTON T. SCOTT. 

